"A couple of friends recently mentioned to me that there is a book that
describes how people's blood type affects their health and diet; apparently
there is one type in particular that just can't be healthy without eating
some meat."

Kent:

It's called "Eat Right 4 Your Blood Type".  I don't have the author's name
but it's pretty popular.  Barnes and Noble have it as well as most health
food stores.  It states that blood type "O" needs to eat meat and limit
consumption of carbohydrates.  It does say that another blood type (don't
remember which one) should stay away from meats because their system isn't
acid enough to digest it.  I found it very interesting reading as I am an
"O" blood type and had been on a vegetarian diet for years.  I feel much
better now that I'm eating meat again.  Haven't gone Paleo all the way but
see myself moving in that direction.  The book certainly isn't promoting
the Paleo diet, but the suggested diet for "O"s is the closest I've seen.

Rose